Another useful type is `SetField` which stores a set instead of a list. On DBs that don't support sets this field can be emulated by storing a list, instead. This is the approach taken by Django-nonrel's App Engine backend.

MongoDB and other databases use `ListField` in combination with `DictField` to completely replace `ManyToManyField` in a lot of cases. Django currently doesn't provide an API for querying the data within a `DictField` (especially if it's embedded in a `ListField`). Ideally, the query API would just use the `foo__bar` JOIN syntax.

The field is already implemented in Django-nonrel, but lookups aren't supported, yet.

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= !EmbeddedModelField =

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== !EmbeddedModelField ==

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This is a field which stores model instances like a "sub-table within a field". Internally, it's just a `DictField` which converts model instances to/from dicts. In addition to the `DictField` issues this field also has to call the embedded fields' conversion functions, which again requires special support if the JOIN syntax should be supported.

The field is already implemented in Django-nonrel, but lookups aren't supported, yet.

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= !BlobField =

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== !BlobField ==

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Many databases provide support for a raw binary data type. Many App Engine developers depend on this field to store file-like data because App Engine doesn't provide write access to the file system (there is a new Blobstore API, but that doesn't yet allow direct write access).